Speaker 1: Hey, please take a second and leave us a review
Speaker 1: on Apple Podcasts, Spotify, or wherever you listen to the podcast.
Speaker 1: Thanks a lot. Hey, welcome to sign Stuff, a production
Speaker 1: of iHeartRadio I'm More cham and today we're looking into amnesia.
Speaker 1: How does it happen, why does it happen, and what
Speaker 1: are some of the most dramatic cases of it in history.
Speaker 1: It's part of a two part series on memory. So
Speaker 1: if you haven't checked out the first episode about super memory,
Speaker 1: go check it out. But in this episode, we're going
Speaker 1: to explore what it means to edge and then erase
Speaker 1: a memory. We're going to learn about a new technology
Speaker 1: that can essentially suppress memories with the push of a button.
Speaker 1: And we're going to look into amnesia and a condition
Speaker 1: called severely deficient autobiographical memory, which once you hear about it,
Speaker 1: you won't be able to forget. So tie a stringer
Speaker 1: on your finger because we are going down a memory
Speaker 1: hole to explore the science of amnesia. Enjoy. Hey everyone,
Speaker 1: Today we're continuing our exploration of memory. In the previous episode,
Speaker 1: we talked about the ability to remember a lot of things,
Speaker 1: and now we're going to focus on we'regetting for example,
Speaker 1: have you ever wondered what happens to a memory once
Speaker 1: you can't remember it anymore? Or why sometimes, usually in
Speaker 1: the worst possible moment, you can't remember an important piece
Speaker 1: of information like your friend's name when you're introducing them
Speaker 1: at a party. And then going further, what's actually happening
Speaker 1: in people with amnesia or people who can't make new memories.
Speaker 1: Have you seen the movie Memento or remember the character
Speaker 1: of Dori and finding Nemo. Well, that actually happens in
Speaker 1: real people. What's it like to be them and how
Speaker 1: are they still able to function? We're going to tackle
Speaker 1: all of these questions, starting with how memories are made
Speaker 1: and how they're forgotten to tell us about the search
Speaker 1: for the basic mechanism of memory. Talk to doctor Sarah
Speaker 1: ro bin, a professor and the co director of the
Speaker 1: Cognition Agency and Intelligence Center at Purdue University. Well, thank you,
Speaker 1: doctor Robbins for joining us.
Speaker 2: Yes, thank you for having me. I am Sarah Robbins.
Speaker 2: I'm a philosopher and cognitive scientist of memory. So I
Speaker 2: study and in particular the science of memory.
Speaker 1: That's good that you remember all that I.
Speaker 2: No longer have to write it down takes a little bit.
Speaker 1: So that's an interesting mix between psychology and philosophy. Can
Speaker 1: you tell us a little bit about that area in between.
Speaker 2: Yeah, and it includes neuroscience very deeply as well, So
Speaker 2: I think of it as sort of different ways of
Speaker 2: researching and thinking about the mind and the brain. Historically
Speaker 2: they were very intertwined, so early psychology was often called
Speaker 2: natural philosophy, and I often see the philosopher's role as
Speaker 2: someone who's paying attention to what every one of those
Speaker 2: is doing and talking about the bigger questions that started
Speaker 2: the science in the first place.
Speaker 1: Feels a little like inceptions. It's like your researching what
Speaker 1: we think of, how we think about, what we're learning about,
Speaker 1: how we.
Speaker 2: Think, yes, exactly, that's fun.
Speaker 1: Okay. According to doctor Robins, scientists have been trying to
Speaker 1: figure out how the brain records memories for a long time.
Speaker 1: It's been a search for what scientists call the n gram.
Speaker 2: So an ingram is really the neural mechanism that makes
Speaker 2: remember impossible or by which memories are supported so that
Speaker 2: they can later be remembered.
Speaker 1: Okay, like how the brain stores information? Yeah, and I
Speaker 1: guess for a long time people have been wondering like,
Speaker 1: how does that work in the brain?
Speaker 2: Exactly? Yeah, how is it? Where is it? Like what
Speaker 2: could possibly be the case? So the zoologists that coined
Speaker 2: the term, Richard Demmon, she first wrote the book where
Speaker 2: he coined the term in nineteen oh four in German.
Speaker 2: He's calling it like it's somewhere in the irritable substance,
Speaker 2: which is how people thought about the kind of material
Speaker 2: of the brain at the time, which I just disagree.
Speaker 1: That's well, unfortunately I have a lot of irritable substance
Speaker 1: in my brain we all, especially in the mornings.
Speaker 3: Yes, it's especially irritable.
Speaker 2: Then, absolutely there.
Speaker 1: So we've been looking for how the brain stores memories
Speaker 1: for over a hundred years now. You might think, why
Speaker 1: has it taken so long? Can we just open up
Speaker 1: a brain and see what's going on? Well, it's not
Speaker 1: that easy.
Speaker 2: One is a challenge that is, like it's hard to
Speaker 2: know what's in your memory outside of actually like being
Speaker 2: able to look in there. Right, So if you can't
Speaker 2: remember something, it's kind of a question of like is
Speaker 2: it in there but you can't get it out?
Speaker 3: Or is it not in there?
Speaker 2: But like how do you tell Like how do we
Speaker 2: know what's really in there until we get it out.
Speaker 1: Yeah, it just made me realize what a difficult problem
Speaker 1: this is because I think we're all familiar with memories.
Speaker 1: We all have memories, we all remember things, but like,
Speaker 1: how do you do an experiment on to figure out
Speaker 1: how it works inside a brain as it's happening.
Speaker 2: Absolutely, And I think that's why some of these memories,
Speaker 2: like when they come to you kind of out of nowhere,
Speaker 2: are so delightful. Like when you hear a song you
Speaker 2: haven't heard for twenty years and you remember all the word.
Speaker 2: You can have this kind of like oh my gosh
Speaker 2: sort of reaction to that. Oh it was in there,
Speaker 2: and you sort of had no idea that it was there. Right,
Speaker 2: It's not like I can like, oh, what other fun
Speaker 2: stuff isn't there? Like I'm not going to know until
Speaker 2: that happens again.
Speaker 1: Yeah, that is so tricky. In other words, it's hard
Speaker 1: to study how the brain stores memories because you can't
Speaker 1: just poke around someone's brain while they're making a memory
Speaker 1: or trying to remember something. But all of that changed
Speaker 1: about ten to fifteen years ago with the development of
Speaker 1: a technology called optogenetics. I'll explain what that technology is
Speaker 1: a little later. But first, here's what we've learned after
Speaker 1: a century of science, but how the brain records a memory.
Speaker 1: So you wrote in a paper that we found the nngram.
Speaker 1: What does that mean that we've found it?
Speaker 2: I think it's now the case that it's possible to
Speaker 2: identify the set of neurons that are active in storing memories.
Speaker 1: We'll step me through this. So I am walking around
Speaker 1: and something incredible happens. The unicorn jumps out of the
Speaker 1: manhole and then grows wings and flies off into the sky.
Speaker 1: I'm definitely going to remember that. What's happening in my brain?
Speaker 3: Yes, So what's happening?
Speaker 1: I mean, I'll give you a second to process that image.
Speaker 1: I just.
Speaker 2: Well, the unicorn area of processing and the manual air
Speaker 2: and not there yet. So there's a set of cells
Speaker 2: in the hippocampus and surrounding structures that are kind of
Speaker 2: responsible for being the ones that react to that experience
Speaker 2: and kind of encode information about that experience in somewhay,
Speaker 2: there's a whole lot of neurons in that area, and
Speaker 2: a subset of them are going to say, like we've
Speaker 2: got this one here. You know, we're going to take
Speaker 2: hold of that and something about the way that they
Speaker 2: activate together capture something about that events.
Speaker 1: All right, So I see the unicorn. There are some
Speaker 1: cells among the many, many, many many in my hippocampus
Speaker 1: that are like I'm ready, I'm ready to remember things.
Speaker 1: And then I see the unicorn. And it's what happens
Speaker 1: to those cells. They sort of like change, they something
Speaker 1: what happens.
Speaker 2: So they like become better connected to each other. I'm
Speaker 2: not sure how far I can go with this metaphor,
Speaker 2: but this is just like a sea of willing people
Speaker 2: to play on the team for whatever sport you have.
Speaker 2: Each time there's an experience, you like send a team
Speaker 2: out and like they play together and they kind of
Speaker 2: form a bond that makes them a team that is
Speaker 2: about the experience.
Speaker 1: They lock hands, they're like, we got this memory. We're
Speaker 1: going to remember that unicorn. We are the unicorn in
Speaker 1: your head.
Speaker 2: We got it exactly. And then they kind of go
Speaker 2: back into the sea and you bring out a new
Speaker 2: set to play the next game and they do their connecting.
Speaker 1: So that, in a nutshell, is what we know about
Speaker 1: how the brain records a memory, or at least a
Speaker 1: memory of an event. There's an area in your brain
Speaker 1: called the hippocampus, which sort of looks like two small
Speaker 1: jalapeno peppers buried deep inside your with millions of neurons
Speaker 1: in it, all connected to each other. And when something
Speaker 1: memorable happens, some of those neurons, maybe a few hundred
Speaker 1: of them, kind of get activated and they step up
Speaker 1: to remember the event, and they do it by strengthening
Speaker 1: the connections between them, which are called synopsis. The synopsis
Speaker 1: get stronger, which means that network of cells is more
Speaker 1: likely to activate together. As doctor Robin said, a good
Speaker 1: analogy is to imagine a stadium full of people, and
Speaker 1: when a new memory has to be recorded, as subset
Speaker 1: of those people step up and they lock hands and
Speaker 1: somehow that stores the memory. Okay, two quick things about that. First,
Speaker 1: a neuron can be a part of multiple memories, not
Speaker 1: just one.
Speaker 2: And it's possible over time that some of these cells
Speaker 2: will play on different teams.
Speaker 1: Right, It's like I'm the unicorn cell with these group
Speaker 1: of cells, but with these group of cells, I am
Speaker 1: the I am the purple crocodile, or is another.
Speaker 3: Day exactly exactly And.
Speaker 1: Two that's what we see happening in the hippocampus during
Speaker 1: an event, but we don't actually know if that's where
Speaker 1: the memory is stored. Is a hippocampus kind of like
Speaker 1: the hard drive of the brain, or is it more
Speaker 1: like the relay of the brain, or like what's happening?
Speaker 3: I think that's a question of live debate.
Speaker 2: So it could be that it's individually storing each memory
Speaker 2: and holding them and they stay in the hippocampus long term.
Speaker 2: That is a view that some people hold. It could
Speaker 2: be that it is just kind of a relay, like
Speaker 2: it's the place that keeps tags or recipes, right, but
Speaker 2: all the content is distributed elsewhere.
Speaker 1: Okay, that's what we know about how memories are formed.
Speaker 1: Now the question is how do memories get forgotten and
Speaker 1: what's happening in people with amnesia. We'll get to that,
Speaker 1: but first I wanted to dig deeper into how we
Speaker 1: know this is how memories are formed, because the answer
Speaker 1: is pretty cool. It involves a fairly recent technology called optogenetics,
Speaker 1: which basically lets you control memories with the push of
Speaker 1: a button.
Speaker 2: And so that's changed in the last few decades thanks
Speaker 2: to a range of sort of technological tool innovations. A
Speaker 2: central one of which is something called optogenetics, which is
Speaker 2: a technique for making neurons responsive to light. So, colloquially speaking,
Speaker 2: you're putting a light switch on neurons. You make it
Speaker 2: so that you can turn them on and off in
Speaker 2: a living, behaving organism. So you can make certain neurons
Speaker 2: fire action potentials, make them active, or you can inhibit
Speaker 2: them keep them from firing action potentials. Wow, it's incredible.
Speaker 1: Okay, we can probably spend the whole episode just on
Speaker 1: this technology because it's pretty wild. Basically, scientists can now
Speaker 1: hack into the DNA of neurons and make it so
Speaker 1: that when the neurons are activated, they produce a protein
Speaker 1: that makes the neurons sensitive to light, and scientists can
Speaker 1: time when this happens so that it only happens to
Speaker 1: neurons in a specific brain area and during a specific event. So,
Speaker 1: for example, you could make it so that everything you
Speaker 1: experience in the next hour or so gets etched into
Speaker 1: neurons in your hippocampus, and any neurons that get recruited
Speaker 1: to remember those memories become light sensitive to you. Nothing
Speaker 1: would change, You would simply have that memory as you
Speaker 1: normally would. But now if I take a tiny fiber
Speaker 1: optic flashlight and I thread it into your brain and
Speaker 1: turn the light on. Those neurons that recorded that memory
Speaker 1: would turn on and you would suddenly and involuntarily get
Speaker 1: a flashback of what happened. And if you press the
Speaker 1: button again, those neurons would activate again and you would
Speaker 1: get a flashback again. Essentially, you could relive that memory
Speaker 1: by just pressing that bun and scientists can also do
Speaker 1: the reverse, which is to make to produced proteins that
Speaker 1: make them stop working when they sense light. So you
Speaker 1: could do the opposite, which is to make a memory
Speaker 1: and then suppress that memory by simply turning on the light.
Speaker 1: The scientists could make you forget something you just saw
Speaker 1: by simply pushing on a button. It's pretty wild stuff,
Speaker 1: and it involves things like immediate early genes and special
Speaker 1: antibiotics to suppress these genes, which we don't have time
Speaker 1: to cover this, but this is essentially what has unlocked
Speaker 1: a lot of the memory research in the last ten years.
Speaker 1: I didn't know we were that advance in this kind
Speaker 1: of manipulation of neural activity.
Speaker 2: It's absolutely incredible to see what sorts of work could
Speaker 2: be done in this way. And there are people that
Speaker 2: have been using these similar techniques to sort of figure
Speaker 2: out which neurons are trying to be a part of
Speaker 2: the memory, and you can kind of follow them around
Speaker 2: and again find the ngram in this way and then
Speaker 2: activate and manipulate it.
Speaker 1: Okay, that is how we make memories. When we come back,
Speaker 1: we'll get to the ession of how we forget memories
Speaker 1: and what's happening in the brain of people with amnesia
Speaker 1: and something called severely deficient autobiographical memory. We'll get to
Speaker 1: all of that, So don't blink out. Lock in this memory.
Speaker 1: We'll be right back. Hey, welcome back. We're talking about
Speaker 1: the size of amnesia, and so far we've talked about
Speaker 1: how the brain makes memories. Now we're going to talk
Speaker 1: about how the brain forgets memories. As it turns out,
Speaker 1: there's a big mystery about how we actually forget that
Speaker 1: scientists haven't figured it out. To take us through this,
Speaker 1: here's doctor DANIELA. Palombo, Professor of psychology at the University
Speaker 1: of British Columbia. Well, thank you doctor Palombo for joining
Speaker 1: us again.
Speaker 3: Yeah, my pleasure.
Speaker 1: So I thought it'd be interesting to talk about the
Speaker 1: absence of memories what are some of the different ways
Speaker 1: that we can lose memories.
Speaker 4: Yeah, that's a really good question. So I guess I'll
Speaker 4: start by saying that any of us can lose our memories.
Speaker 1: Okay. According to doctor Palombo, there are several kinds of
Speaker 1: memory loss. First is the casual kind that we all
Speaker 1: experience every day in our memory slips.
Speaker 4: So in our day to day lives, you know, whether
Speaker 4: we're young or older, we see that we experience memory
Speaker 4: slips where we think we should have access to something
Speaker 4: we don't, and that happens to all of us all
Speaker 4: the time. I'm sure you've experienced this many times. And
Speaker 4: so I have a very vivid memory of a time
Speaker 4: where I was introducing a bunch of people at a
Speaker 4: party and I had a coworker over who I knew
Speaker 4: very well, and I just temporarily forgot my coworkers seeing
Speaker 4: and he was staring at me in shock and disbelief,
Speaker 4: and I was also very very surprised and embarrassed, and
Speaker 4: then you know, a few minutes later, it popped back
Speaker 4: into my mind. So that type of loss refers to
Speaker 4: temporary and access to information, and it certainly happens as
Speaker 4: we get older and This is all part of healthy aging.
Speaker 1: I see, are you still friends with this person or
Speaker 1: that relationship?
Speaker 3: They did forgive me thanks leady.
Speaker 1: They forgot about it. Well, this makes the question about
Speaker 1: in the situations where we can get at a memory,
Speaker 1: but later on we remember, like what happens there? Like
Speaker 1: where does that memory go that I can't excess it?
Speaker 4: So sometimes it's simply due to interference. So we're in
Speaker 4: a situation where we're just not searching for the memory
Speaker 4: in the right way, and then later on something in
Speaker 4: our environment might trigger that memory. Sometimes it's because we're
Speaker 4: feeling very stressed. It can be feeling a bit anxious
Speaker 4: in the moment.
Speaker 1: So that's a memory slip where we have temporary trouble
Speaker 1: accessing a memory. There's also just forgetting something over time.
Speaker 1: Is there just plain forgetting? Like is it possible for
Speaker 1: me to have stored a memory in my brain cells
Speaker 1: but over time they just sort of, you know, like
Speaker 1: the hard drive gets corrupted or erased.
Speaker 4: Yes, so forgetting is a pretty loaded term. But you're
Speaker 4: right that we can form memories and then over time
Speaker 4: those memories become difficult to access. And one hypothesis is
Speaker 4: that that's because there's lots of interfering new information that
Speaker 4: we're encoding and needing to retrieve, and so the more
Speaker 4: memories we form over our lifetime, the more competition there is.
Speaker 2: Right.
Speaker 4: Another hypothesis is that just as our lives change and
Speaker 4: we grow, et cetera, the retrieval cues that we use
Speaker 4: to access those really old memories are not as close
Speaker 4: to our fingertips anymore. So you've moved on from your
Speaker 4: childhood home, et cetera, so it's harder to access those memories.
Speaker 1: I see, you sort of lose the path to those memories.
Speaker 3: Yeah, exactly.
Speaker 1: So some things you can lose a memory because you
Speaker 1: lose a connection to it. It's still in your brain,
Speaker 1: but because it's simply not relevant to you, you never
Speaker 1: find your way to it again. Now, memory slips and
Speaker 1: losing connections to your memories over time are both natural processes.
Speaker 1: They happen to anyone. But now we get to the
Speaker 1: kind of memory loss that's due to something specific.
Speaker 4: And that can happen in the context of disease. So
Speaker 4: you've probably heard about different forms of dementia, like Alzheimer's disease,
Speaker 4: where you can see quite profound, albeit progressive memory loss.
Speaker 4: And then there's another condition called amnesia. Then this is
Speaker 4: often due to a brain injury of virus. It can
Speaker 4: happen in the context of a stroke, and here.
Speaker 1: We get to amnesia. Now, the thing about amnesia is
Speaker 1: that it typically happens because of an event. It could
Speaker 1: be a stroke or a traumatic brain injury, or sometimes
Speaker 1: it's a virus that infects your brain. Whatever the cause,
Speaker 1: most cases of amnesia have something in common.
Speaker 4: Yeah, lots of different causes to amnesia, but one thing
Speaker 4: that they have in common is that they affect really
Speaker 4: similar networks in the brain. And there's one area of
Speaker 4: the brain in particular that's quite vulnerable to whether it's
Speaker 4: a virus or certain kinds of stroke, certain kinds of
Speaker 4: traumatic brain injury, et cetera, epilepsy, and that's a region
Speaker 4: of the brain called the hippocampus. And so when that
Speaker 4: area of the brain is affected, regardless of the cause,
Speaker 4: you see a profound loss of memory.
Speaker 1: Yes, the thing most cases when anesia have in common
Speaker 1: is that they affect the hippok campus. Now, once the
Speaker 1: hippocampus's damaged, two basic things can happen. One, you can
Speaker 1: lose past memories that you had before the event the
Speaker 1: damage to hippocampus. For example, childhood memories, the names of people,
Speaker 1: those could all be gone. And two, you can also
Speaker 1: lose the ability to make new memories after the event,
Speaker 1: and both of these kinds of anesia have different names.
Speaker 1: Using memories you had before the event is called retrograde anesia,
Speaker 1: and losing the ability to make new memories is called
Speaker 1: terograde anesia. You're probably familiar with these kinds of anesia
Speaker 1: just from popular culture. In a soap opera, when someone
Speaker 1: has an accident and they can't remember who they are
Speaker 1: or anything about their history, that's retrograde anesia. And in
Speaker 1: the movie Memento or with Dory and Finding Nemo, where
Speaker 1: the character seems to forget everything that happens to them
Speaker 1: and everything seems new to them, that's anterograde anesia. Now,
Speaker 1: there are a couple of fascinating things to talk about
Speaker 1: in each of these kinds of anesia. We'll start with
Speaker 1: retrograde anesia, where you lose your past memories. The fascinating
Speaker 1: thing is that scientists aren't really sure if you actually
Speaker 1: lose your memories.
Speaker 4: Yeah, so this is a question that a lot of
Speaker 4: memory scientists have what does it actually mean to have
Speaker 4: loss of memory? And so the one hypothesis is that
Speaker 4: the places in the brain where the memories are stored
Speaker 4: are damaged and so those memories are gone. And another
Speaker 4: hypothesis that you're getting at is that the memories are
Speaker 4: still stored somewhere in the brain, but via damage to
Speaker 4: the hippocampus, those memories cannot be accessed.
Speaker 1: Wow, So the memories are still.
Speaker 4: In there potentially potentially Yeah, Because remember last time we spoke,
Speaker 4: I sort of described this idea that the hippocampus in
Speaker 4: particular is a pointer to different parts of the brain
Speaker 4: where the memories are kind of stored within a network,
Speaker 4: and so when that index pointer is not working anymore,
Speaker 4: those memories are not accessible. Now we don't know for sure,
Speaker 4: because there's a lot about memory and the brain that
Speaker 4: we don't yet understand, but that is one idea that's
Speaker 4: been put out there.
Speaker 1: Yes, if you have retrograde amnesia, your memories might still
Speaker 1: be intact in your brain and what you lose is
Speaker 1: actually the ability to access them, although that doesn't mean
Speaker 1: you could get them back.
Speaker 4: Some cases, like in soap operas for example, sometimes it
Speaker 4: does involve an injury to the head, and so you'll
Speaker 4: see a situation where somebody got bonked on the head.
Speaker 4: They can't remember anything, including who they are, for a
Speaker 4: period of time, and then oftentimes they get bonked on
Speaker 4: the head again and that sort of shakes them out
Speaker 4: of the amnesic syndrome. And so that's not an accurate
Speaker 4: depiction of what looks like.
Speaker 1: Oh no. Now, for people with anterograde amnesia, or the
Speaker 1: inability to make new memories, there are two fascinating things
Speaker 1: about them. The first is that because they can't make
Speaker 1: new episodic memories, they live in a constant state of surprise,
Speaker 1: as if they are just waking up every so often,
Speaker 1: because anything that's happened to them recently they don't remember.
Speaker 4: What we tend to see is this kind of profound
Speaker 4: loss of episodic memory. And that's kind of the most
Speaker 4: striking feature of amnesia. And what I mean by that
Speaker 4: is if you're sitting with an m music participant and
Speaker 4: you're having a conversation and you leave the room for
Speaker 4: a few minutes and you return, they're not necessarily going
Speaker 4: to remember that conversation. They're not going to remember that
Speaker 4: you met them, what you talked about, et cetera, and
Speaker 4: they also have difficulty remembering new facts, even though they
Speaker 4: actually can access semantic memories from before their injury, so
Speaker 4: they know who they are, they know lots about the world,
Speaker 4: et cetera.
Speaker 1: One of the most extreme examples of this kind of
Speaker 1: amnesia is a man named Clive Wearing. He's still alive today.
Speaker 1: He's eighty seven years old now, but when he was
Speaker 1: forty seven, a virus got into his brain and destroyed
Speaker 1: a lot of his hip hook campus. This prevents him
Speaker 1: from remembering anything that happens beyond about seven seconds. So
Speaker 1: you can have a conversation with him, but after a
Speaker 1: short while, he won't remember who you are, what you
Speaker 1: were talking about, or even how he got to the
Speaker 1: place where he is right now now. Before the virus,
Speaker 1: mister Wearing was a musicologist and an orchestra conductor, so
Speaker 1: he still remembers how to play music, and he also
Speaker 1: remembers his wife and the fact that he has kids,
Speaker 1: but he only remembers his kids from when they were little.
Speaker 1: Try to imagine what it would be like to be yourself,
Speaker 1: but to find yourself in a constant state of not
Speaker 1: knowing where you are or how anything around you got
Speaker 1: to where it was we're not being able to recognize
Speaker 1: any of the people around you, even though they act
Speaker 1: perfectly normal, as if they've been hanging out with you
Speaker 1: for a while. It's pretty mind boggling. But here's the
Speaker 1: other fascinating thing about people with anteror grade amnesia. They
Speaker 1: can often still learn new skills. We'll get to what
Speaker 1: that means and how we know that after the break.
Speaker 1: Stay with us, we'll be right back. Hey, welcome back.
Speaker 1: We're talking about the science of forgetting, and so far
Speaker 1: we talked about anesia and the different kinds of it.
Speaker 1: There's a kind where you don't remember memories you had
Speaker 1: before the injury that caused the amnesia. That's called retrograde amnesia.
Speaker 1: And there's a kind where you can't make new memories
Speaker 1: starting from the time of the injury. That's called anterograde amnesia.
Speaker 1: And we also talked about several fascinating things about each
Speaker 1: of these kinds. Now, another fascinating thing about anterograde amnesia,
Speaker 1: where someone can't make new episodic memories like in the
Speaker 1: movie Memento or Dory from Finding Nemo, came from one
Speaker 1: of the first cases of this kind of anesia ever studied,
Speaker 1: which was a man named Henry Mollison. Henry Mollison, Yeah,
Speaker 1: the famous patient HM.
Speaker 4: Yes, exactly. So he was studied for many decades and
Speaker 4: this first began in the nineteen fifties. So he had
Speaker 4: a surgery in nineteen fifty three to remove parts of
Speaker 4: the brain that are really important for memory, such as
Speaker 4: the hippocampus as well as the surrounding medial tempor lobe structures,
Speaker 4: and all of that was removed in HM in this
Speaker 4: surgery to help relieve intractable epilepsies. So after HM surgery,
Speaker 4: at first blush, it appeared that the removal of this
Speaker 4: tissue had kind of little impact on his cognition, but
Speaker 4: it soon became clear that his memory was sort of
Speaker 4: somewhat selectively and deeply affected.
Speaker 3: He was profound me in music.
Speaker 1: So Henry Mullison had severe and terror grade amnesia, just
Speaker 1: like dor and finding Nemo or Clive Wearing the music
Speaker 1: conductor I talked about before, if you met Henry, he
Speaker 1: would forget about you within a few minutes of meeting you,
Speaker 1: which meant he lived in a constant state of not
Speaker 1: knowing where he was or how he got there, But scientists,
Speaker 1: namely a researcher called Brenda Milner, soon figured out something amazing.
Speaker 1: Henry could learn new skills.
Speaker 4: Come into the laboratory, and he'd be given a new
Speaker 4: skill task, but he wouldn't remember ever having been exposed
Speaker 4: to the task. He'd come in day after day and
Speaker 4: he would perform it as though it was a brand
Speaker 4: new task for him, even though he was getting better
Speaker 4: over time.
Speaker 1: So scientists learned they could teach Henry new skills, but
Speaker 1: he wouldn't remember having learned those skills. For example, you
Speaker 1: could teach him to play the piano or to play tennis,
Speaker 1: and he wouldn't remember taking the lessons, But the next
Speaker 1: time he would sit in front of a piano or
Speaker 1: pick up a tennis racket, he'd be amazed that he
Speaker 1: knew how to use them. And this is because, as
Speaker 1: we talked about before, there are different kinds of memory
Speaker 1: in your brain. Remembering things that happened to you, or
Speaker 1: the fact that you took music or tennis lessons are explicit,
Speaker 1: episodic or semantic memories, but knowing how to hit the
Speaker 1: keys on a piano or how to swing a tennis
Speaker 1: racket are implicit motor memories. This case of Henry Mullyson
Speaker 1: unlocked a lot of what we now know about the
Speaker 1: different memory systems in our brain. Now, I talked about
Speaker 1: the two basic kinds of anesia, losing old memories and
Speaker 1: not being able to form new memories, as if there
Speaker 1: are different kinds of anesia, and they are, but according
Speaker 1: to doctor Palombo, they often happened together. Patient HM Henry
Speaker 1: Mollison had both, as well as Clive Wearing and Dori
Speaker 1: in finding Nemo. Okay, we're now going to get to
Speaker 1: the last kind of forgetting, which is a condition called
Speaker 1: severely deficient autobiographical memory. According to doctor Palombo, this is
Speaker 1: similar to interrograde anesia, except it's a condition that some
Speaker 1: people seem to be born with.
Speaker 4: So I did some work on what we refer to
Speaker 4: as severely deficient autobiographical memory. And my work on STAM
Speaker 4: was done in collaboration with doctor Brian Levine, and we
Speaker 4: studied a group of three individuals who contacted us and
Speaker 4: shared with us that they had profound difficulty or even
Speaker 4: an inability to vividly recollect events from their past wow,
Speaker 4: but were otherwise healthy and high functioning. And so we
Speaker 4: brought these individuals into our lab and we studied them
Speaker 4: for a few years, and we studied the way that
Speaker 4: they remember episodes to you know, try to see what
Speaker 4: we can sort of understand about memory from studying these
Speaker 4: individuals who fall at the kind of other end of
Speaker 4: the extreme to that of age SAM, who are as
Speaker 4: we remember, people who remember quite a lot.
Speaker 1: Okay, if you remember, in our last episode about super memory,
Speaker 1: we talked about people with something called highly superior autobiographical
Speaker 1: memory or h SAM, who could remember everything that's ever
Speaker 1: happened to them in their lives. Well, people with severely
Speaker 1: deficient autobiographical memory or as DAM, are sort of the
Speaker 1: opposite of that condition. They can't remember anything that happens
Speaker 1: to them.
Speaker 4: And so I'll say early days with us as it
Speaker 4: is with h SAM, And so our scientific understanding of
Speaker 4: SDAM is quite limited. But what we do know so
Speaker 4: far is that it seems like individuals with SDAM access
Speaker 4: their past in a different way. And so rather than
Speaker 4: reliving episodes from their past in vivid and rich detail,
Speaker 4: they tend to access their past more through semantic remembering.
Speaker 1: I see it. Could you describe the condition, like what
Speaker 1: is it like for them?
Speaker 4: So it kind of depends on the person, and so
Speaker 4: some people will describe having difficulty accessing visual images through
Speaker 4: their memory. And so it's mainly that this sort of
Speaker 4: conscious access to reexperiencing the past is limited or absent.
Speaker 4: But yet nonetheless they can access their knowledge about the
Speaker 4: world and through facts. And so oftentimes you'll hear individuals
Speaker 4: with SDAMS say that they just know their past, but
Speaker 4: they're not reliving it in that sort of rich episodic format.
Speaker 1: Like I remember I went to college at the University
Speaker 1: of Toronto, but I have no memories of being there
Speaker 1: or what it was like exactly.
Speaker 4: Yes, the episodes that can be relived.
Speaker 1: Yes, there are people out there that can remember facts
Speaker 1: about their lives, but they don't actually remember living it.
Speaker 1: They don't seem to be able to record the kind
Speaker 1: of memory that lets you relive your past. They know
Speaker 1: they were there, but they don't remember being there. Uh.
Speaker 1: It's like I know I had a kid, and I
Speaker 1: know they were really young, but I have no memories
Speaker 1: of those early days taking care of newbore.
Speaker 3: Yes, exactly.
Speaker 4: And so you have lots of information about your lives,
Speaker 4: about your loved ones, et cetera, but it's just you're
Speaker 4: not accessing that information through episodic memory.
Speaker 1: Uh, like my record button just wasn't on.
Speaker 4: Possibly it could be that the record button was on,
Speaker 4: but it's a different pathway towards accessing those memories. So
Speaker 4: that could be right from the get go, that memories
Speaker 4: are being laid down in a more factual conceptual way.
Speaker 4: That's a very open question.
Speaker 1: Oh, I see they might have the record but on,
Speaker 1: but maybe the camera works a little bit different.
Speaker 3: That's right exactly.
Speaker 1: I see, what do you think and this might not
Speaker 1: be a scientific question, but what is it like too?
Speaker 4: Yeah, so I think you're asking a little bit about
Speaker 4: sort of what the lived experience of ASBM is.
Speaker 1: Yeah.
Speaker 4: I think that's such an important question. And I think
Speaker 4: as scientists sometimes we get wrapped up in studying the
Speaker 4: nuts and bolts of what memory might look like in
Speaker 4: a particular group of individuals, and I think it's important
Speaker 4: to take a step back and think about what those
Speaker 4: lived experiences are like for our participants. Anecdotally, I guess
Speaker 4: I'll say that for some individuals, lacking this re experiencing
Speaker 4: component of memory can be hard for them and for
Speaker 4: others less so. And so I think in the individuals
Speaker 4: we studied, they were high functioning in terms of their
Speaker 4: day to day and they were by all accounts healthy.
Speaker 4: You know, I think that individuals with STAM feel in
Speaker 4: the moment probably as richly and profoundly as the rest
Speaker 4: of us do. But it could be that just the
Speaker 4: way that one reflects on their past, that there's individual
Speaker 4: differences there. So it could be that when you don't
Speaker 4: have access to the past in terms of re experiencing episodes,
Speaker 4: it might help you move on from the past when
Speaker 4: things were difficult.
Speaker 1: This brings us to the last question I had for
Speaker 1: doctor Palumbo, which is, why do we forget in the
Speaker 1: first place. If it's possible to remember everything that happens
Speaker 1: to you in your life, as some people would super
Speaker 1: memory prove, why didn't we all evolve disability to remember everything?
Speaker 1: What's the point of forgetting?
Speaker 4: Yes, exactly. And that might seem strange because we would
Speaker 4: hope that our memory systems would be a perfect record
Speaker 4: the past. That would be really helpful in many situations.
Speaker 4: But in fact, memory researchers would argue that it is
Speaker 4: actually adaptive to forget, and we sort of have this
Speaker 4: sweet spot of remembering just enough so we live. We
Speaker 4: are encoding experiences at every moment, and a lot of
Speaker 4: things repeat in our environment, so we're picking up patterns
Speaker 4: in the world, and it's that kind of information that's
Speaker 4: really useful to us when we're thinking about decisions we
Speaker 4: need to make in the moment or planning out our future,
Speaker 4: et cetera. So we actually think that having an imperfect
Speaker 4: memory system, a memory system that's flexible and reconstructive, is
Speaker 4: actually really good for us.
Speaker 1: Yeah, I guess the idea is that your memory is
Speaker 1: meant to be a little fuzzy so that you can
Speaker 1: see the larger patterns in your life.
Speaker 3: Yeah, that's a really good way to put it.
Speaker 1: So you don't miss the forest for the trees.
Speaker 4: Kind yes, exactly exactly, because we all didn't have to
Speaker 4: make really quick decisions, especially if we're being threatened by something,
Speaker 4: and so we want to know how things generally occur,
Speaker 4: not necessarily how they occurred just once.
Speaker 1: I see, like, we don't get hung up on whether
Speaker 1: the tiger running at you have the same stripes as
Speaker 1: the last tiger you saw a few weeks ago. You
Speaker 1: just want to remember it it's a tiger. At least
Speaker 1: you run away.
Speaker 3: That's exactly right.
Speaker 1: Yes, oh interesting, So there's a reason I'm forget that.
Speaker 1: What we're saying, there's there's a good reason, very.
Speaker 3: Good reason you're forgetful.
Speaker 1: Yeah, yeah, all right. That was a lot of information
Speaker 1: about memory, amnesia and forgetting. But the good news is
Speaker 1: that if you don't exactly remember the things we talked about,
Speaker 1: you can just get the replay button and you'll get
Speaker 1: to relive these conversations all over again. It's like our
Speaker 1: phones and our computers are now part of our extended memory.
Speaker 1: Thanks for joining us, don't forget to come back next week.
Speaker 1: See then you've been listening to science Stuff. The production
Speaker 1: of iHeartRadio written and produced by me Or Hitcham, edited
Speaker 1: by Rose Seguda, executive producer Jerry Rowland, and audio engineer
Speaker 1: and mixer Kasey Pegram. And you can follow me on
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